Coated sheet metal and process of making the same



April 7, 1936 R; J.,wEAN 2,036,615

COATED SHEET METAL'AND PROCESS OF MAKING THE SAME Filed' Feb. 20, y19:54

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Patented Apr. 7,y 19376 PrvlEN'r'v oFFicE COATED SHEET M'ETAL ANDPROCESS 0F MAKING THE SAME Raymond J. Wean, Warren, Ohio, assignor to4 The Wean Engineering Company, Inc., Warren, Ohio, a corporation of Ohio 'Application February 20, 1934, 'SerialNm 712,160* s'claimrs. (c1. 917o.2)

This invention relates to coated sheet metal and is particularly advantageous where the metal is in strip form. Y

lFerrous sheet metal with a protective coating, as, for example, of lead, tin or zinc,has a wide variety of uses, among which may be mentioned roofing, .buildingl siding, culverts, silver vtin coated sheets for baking pans, etc. Sheets of relatively limited length produced by the Welsh process and strips produced by hot rolling or a combination of hot and cold rolling form the base metal for these products. It is generally necessary to 'subject the base metal to cleaning processes so that the coating "metal will adhere over the entire surface. In those cases where the required coating is of considerable thickness, as, for example, in' culvert stock, the cleaning process is very drastic and usually involves the expendifure of a large amount of time in order to get suiiicient cleaning. The cleaning is generally eiected in any case by a pickling bathand this has disadvantages in that the process is a dirty and disagreeable one andY is not uniformly eilicient unless very carefully controlled. Pickling often .adversely .affects 'the base material causing hydrogen inclusions, which are a fruitful cause of defects such as blisters.

Continuous coating processes have heretofore been proposed but have not been successful, and I believe that a large part of theY dimculty encountered has arisen vfrom the manner of cleaning the base material, f

By my invention itis possible to coat sheetv like material either in long or short lengths with a coating metal such as lead, tin or zinc and to obtaina highly superiorl product. Instead of pickling, I use surface blasting in order to clean the base metal. I thereby obtain a roughened surface peculiar to such process, which Ysurface I have found is ideal for receiving the coating metal. I have found `from tests that the'coating.

adheres very firmly to such a base and permits of crimping or bending the metal to a marked degree without peeling of the coating. This is an exceedingly. important consideration commercially.

.I employ centrifugal means for discharging the cleaning or abradingl agent. Shot blasting of various articles, as, for example, castings, is of course well known, but the general .practice has been to use air as a carrying-medium for the particles. I have .found that this is very undesirable f or lthe cleaning-of sheet metal intended -to 4be used as a base for coating. The amount Io f material to be blasted in a commercial operation is so large that vthe cost of compressed air is generally prohibitive; but entirely apart lfrom this it is undesirable to use an air-borne blasting medium because of the Aeffect on the product. There is always a strong tendency toward the condensationof moisture around compressed air operations, and this is particularly marked on the surface of sheets which have been blasted by an air-l borne abradant. There is always danger of corrosion to some degree between the time the sheets are blasted and the time they are immersed in the coating bath, and there is also danger of minute quantities of Water collecting in the small pits resulting from the blasting, which moisture prevents continuous adherence of the coating to th ba'se metal.

' In the accompanying drawing illustrating present preferred embp'diments of my invention,

Figu l is a diagrammatic view illustrating the rolling of a strip of ferrous metal constituting the base of my improved coated article;

Figure 2 is a diagrammatic view of a centrifugal blasting device for cleaning the surfaces of such material; l l

Figure 3 is a transverse view thereof; Figure 4 is a diagrammatic view showing the coating apparatus;- f

Figure 5 is a transverse view to enlarged scale showing the mannerv in which the edge'of the metal is protected; n

Figure 6 is a view similar to Figure 5 but showing different surface treatments for the two sides of the material; f t .t

Figure 7 is a View showing-my improved product applied to a roof; and

Figure ,8 is a view showing another application of the product for a roof covering.

Referring to' Figure 1, there is illustrated more or less diagrammatically a continuous mill consisting of two-.high stands 2 and four-high roller yj bearing stands 3 for the hot rolling of a slab 4 into a coil of stripmetal 5. ADepending on the desired iinal gauge, this lmaterial may be substantially cold rolled. It is desired that the base` material ultimately obtainedshall have the width and gauge of a sheet and the unlimited length of a strip. The gauge 'actually employed will de-` pend upon the'use to which the material may be put,l buftas a specific exampleI prefer for roofing m/aterial that the width shall be 34to 36 inches andthe gauge ,shall be from 24.vto, 30.

The length will vary, but I prefer that it shall be in excess of 25 feet. Of course, in certain cases shorter pieces may be rolled, butfor purposes of economy I prefer the longer lengths. It is impossible by the ordinary pack rolling process to roll pieces in excess of 25 feet long, and while I contemplate that in certain aspects of my invention the base material maybe produced by pack rolling, `I prefer the use of long lengths such as are obtainable from thestrip metal. A good example of the value of this may be found in the case of roofing material. 'Ihe general practice has been to make it in lengths of from 8 to.12 feet. The sheets are assembled l cleaned with the apparatus shown 'diagrammatically in-Figures 2 and 3. The material to be blasted is fed from a reel 6 over a table 1a, 'Ib to a gathering Vreel 8. In its passage over the table it is subjected to the action of abrasive particles as indicated at 9 from centrifugal blasting wheels I and II. These wheels, which are more particularly described and claimed in U. S. PatentNo. 1,953,566 granted to Louis D..-Peik on April 3, 1934, are mounted on and driven at high speed by shafts I2 and are supplied with a suitable abradant, such as sand or metal shot, through feed pipes I 3. The abradant is fed to the wheels through a stationary member I4 having an opening extending around a limited portion only The use of the member I4 permits of discharging material around a limited portion only of the periphery of the wheel, as best indicated in Figure 3. 'Ihe effect .of the wheels is to remove lany o'xide or other adherent impurity on the base metal and to removeany high polish which the surface may have, leaving it with a characteristic mat or pebbled finish, the coarseness or fineness of which is determined by regulating the size of ,th grit or shot employed, the speed at which the material is moved through the blasting zone, and therate of feed of abradant. As a specic example I have used number 6 0 steel grit at the rate of 260 pounds per. minute for the surface treatment of hot rolled sheets 28 inches wide. These sheets were moved through the abrading zone at therate of 6 feet per minute.

An important feature of thevinvention" is that the roughened surface thus obtained which isO characteristic of dry surface blasting' is ideal lfor'the reception of protective coatingmetal and material through a molten bath of coating metal.

Figure 4 shows a coating operation in diagram.

file base'bmateriahwith its-,surfacemsuitablyvprepared, as above described, is fed from a coil K through a bosh 16 containing acidulated water,

, the blasting, conditions.

have already been pointed out.

and then around suitable guide rolls into and through a metal pot I'I kept up to temperature by burners. I8. The molten coating metal which, in the preferred form of my invention, may be any one of the groupconsisting of lead, tin and zinc is indicated at I9. It may be desirable, particularly in the case of lead, to preliminarily applya thin coating of tin, although the surface treatment above described causes remarkably goed adherence. The surface of the molten coating metal is protected by a suitable ux as indicated at 20. After leaving the coating bath the strip passes through exit rolls 2I and thence over a guide roll 22 to a gathering reel 23.

The material is now in condition to be used. As stated, it may be made in extreme lengths and, as in the case of roong or culverts, made to the desired width. This is advantageous in that the edges of the strip have a protective coatingthereon which is not true in the case of pieces which are sheared from coated sheets. -1 In Figure I have indicated the base metal at B and the coating metal at C. It will be noted that the surface S of the base metal is roughened from the abrasion and this greatly facilitates the adherence of the coating metal, depending on the amount of .roughening of the surface. `The roughness may or may not be reflected in the exterior surface of the coated article. In cases where a smooth finish is important a i'lner grain" may be imparted to the surface by controlling Ordinarily it is desirable'for culvert or roofing stock to have some irregularity in the surface because such irregularities permit of applying a heavierv adherent coating. 'One'of the difliculties of present c ulf lvert stock manufacture is that' drastic pickling must be resorted to in order to get the desired roughness of surface. The objections to'pickling It will be found in many cases that it is desirable to have one surface of -the material rougher than another. This is shown inFigurel 6 wherein the top sur- `face S-I has been considerably roughened by the pleasing and desirable appearance thus obtained and in the case of zinc coating it is found that the surface obtained by dry blasting affects the spangle of the -zinc in some degree and 'gives a. product having a very desirable appearance. For billboard use it will be found desirable to have a somewhat roughened surface'as this forms a better base on which posters may be pasted.

Figure '1 shows a roof wherein a single length 'of my improved material is extended from under one eave, vas indicated at 24, across one roof surface 25, over the ridge 26, down the other roof surface 21, and is securedundeigf the eave 28.

There is. thus presented a continuous stripof roongfrom eave to cave, the only joints being betweenadjacent strips. These joints may be seamed or soldered sothat a roof with practically.

ndchanceot leakage is formed. 'Figure shows the roof starting at the lower edge and working secured along vits upper edge as indicated at 33 silver tin finish.

and by its inturned ends as indicated at 34. The exposed and overlapping edges' may be tacked at intervals as by soldering, or may be soldered continuously. It will be understood that the advantages of the-invention may likewise be obtained by running roofing strips from eave to ridge on each side 'of the roof, the ridge being protected by the usual ridge roll. This phase of my invention is also disclosed and claimed in my copending application Serial No. 727,717, dividedA herefrom.

Another use wherein my material has superior qualities is in baking 'pans This type of finish is only procurable at considerable expense by ordinary methods, but by my process it is obtainable merely by seeing to it that the surface of the base metal is fairly Well pebbled by the cleaning blast, and then applying a tin coating suciently thin that the pebbled eiect is not unduly suppressed. The product has a characteristic finish and the surface is capable of retaining a small amount of grease so that bread baked in pans made of such material does not stick in the pans. This material may advantageously be made with one side smoother than the other, the smooth surface being outermost in the baking pan.

Another use to which my material maybe readily put is for fencing. In certain places it is desirable to have a fence which is continuous in character. For example, in certain parts of South America fences made of steel sheets have been proposed as a means of preventing the incursion of grasshoppers. At present the general practice is to take zinc coated sheets and hang them by means of holes punched in one edge on hooks carried by a support, thereby forming a continuous barrier about 28 inches high. It has also been proposed to take pieces of limited length and crimp them end to end to form rolls which are unrolled at the place of use and fastened to spaced supports. My invention permits of Inaking up the material in continuous pieces, hundreds or even thousands of feet long, which pieces may be much more readily handled and provide a superior barrier.

As stated, my improved material may have the unlimitedlength of a strip and the Width and gauge of asheet. It may vary from, say, 12 inches up to any widthobtainable by available rolling equipment. For example, it is possible to produce material up to 72 inches wide. The gauge will depend upon the use to which the material may be put within the usual range of sheet gauges. As indicated, I anticipate that the gauges from 24 to 30 inclusive will be the most useful for roofing. For other purposes lighter or heavier gauges may be used. For example, culvert stock will usually run from 14 to 2O gauge;

Metal within this range of gauges is capable of withstanding within a reasonable amount the 'shocks imparted by centrifugal surface blasting without becoming unduly distorted. The ame-.int

of coating applied is important. It should be suilicient to insure that adequate protection will l A be obtained and yet should not be so heavy as to be unduly expensive. I append hereto a tabulation of preferred minimum coating weights for zinc coatings, the weight stated in the table being having a so-called a total coating expressed in ounces on both sides of a sheet one foot square.

Weight ci Sheet gage coating I prefer that the coating shall not exceed 2.75 ounces per square foot, although this may be exceeded in some instances. Heretofore the maximum weight of the coating has been determined in considerable measure by the amount of deformation to which it is intended the metal shall be subjected, the general rule being that the more heavily coated sheets ycannot be as abruptly bentv as those with lighter coatings. The material of my invention is characterized by a much greater adherence of the coating metal to the base and on this account it is possible to use heavier coatings in those cases where the metal must be sharply bent, thus increasing the life of the metal materially. In the case of tin plate the coating may be as light as 1 ounce per square foot,

If a pickled surface is particularly desired on one side of the material, for some special reason, I may subject it to the usual pickling process and, aft'er drying, blasting one side only in the manner already described. l

While I have illustrated and described preferred embodiments of my invention, it will be under.-

stood that the same is not limited thereto but may be otherwise embodied and practiced within the scope of the following claims.

I claim: l

l. In the manufacture of coated sheet metal, the steps including pickling base metal in sheet form, centrifugally blasting one side only of the. pickled base metal, and coating both sides of the base vwith a protective metal.

2. As a new manufacture, coated sheet metal comprising a ferrous base having one side pickled and the other side blasted, and a, protective metal coating covering both sides.

3. In the manufacture of sheet metal, -the process whichconsists in rolling a ferrous base metal, abrading the rolled surface with a centrifugal blast to provide a mat surface free from hydrogen inclusions and moisture, and then passing the sheet metal through a molten bath of coating metal.

' 4. The method dened by claim 3 wherein only one side of the base is subjected to abrasin .prior to coating.

5. The method defined by claim 3 wherein opposite sides of the base are subjected to dif- '1. The method denned hyelaiml 3 wherein the base metal is subjected to 'abrasion with the scale or oxide resulting from rolling` remainingy thereon.

8. The xethod defined by claim Sfcharacterized by so regulating the thickness of the coatingthat the roughening of the base effected by abrasion shows through the coating.

9.' The-method dened by claim 3 whereinthe base metal ispickled `and then subjected to abrasion on oneside 'only before coating. f'

' RAYMOND J. WEAN.

CERTIFICATE OF CORRECTION.

Patent No. 2,036,615. April 7, 1936.

RAYMOND J. VEAN.

It is herebyfdertified that error appears in the printed specification of the above numbered patent requiring correctionas follows: Page 5, second column, line 5'6, 'claim 2,'a'f`ter "side" insert centrifgally'; 'and that the said Letters Patent should, be 'read with this correction therein that the same may conform to the 'record of the case in the Patent Off'c. Y

Signed and sealed thisu 5th day. of M'ay, A. -D. 1936.

Leslie Frazer (Seal) A Y Acting Commissioner of Patente.

DISCLAIMER 2036,615.-Raymond J. W'ean, Warren, Ohio. COATED SHEET METAL AND PROCESS oF MAKING- THE SAME. Patent dated April 7, 1936. Disclaimer filed October 6, 1938, by the assignee, The Waan Engineering Company, Inc.

Hereby enters this disclaimer to claims 1, 2', 3, 4, 7, and 9 with the exception that your petitioner does not disclaim the subject matter ofolaim 3 in combination with the subject matter of claims 5 and 6 which are dependent thereon and incorporate claim'3 byreference.

' Gazee November 1, 1.938.] 

